What Is High Blood Pressure?

Blood pressure is the pressure of blood against the blood vessel walls as the heart pumps. When someone has high blood pressure(hypertension), the heart and arteries have a much heavier workload. The heart has to pump harder and the arteries are under greater strain as they carry blood.

Having high blood pressure puts someone at a higher risk for stroke, heart attack, kidney failure, loss of vision, and atherosclerosis (hardening of the arteries).

What Causes High Blood Pressure?

The causes of high blood pressure in kids can differ, depending on a child's age. The younger the child, the more likely the high blood pressure is linked to an illness.

In babies, it's usually caused by prematurity or problems with the kidneys (this is most common), lungs, or heart. These can include conditions like bronchopulmonary dysplasia (an immaturity of the lungs in premature babies) or coarctation of the aorta (a narrowing of part of the major blood vessel that carries blood away from the heart).

While hypertension is far more common in adults, experts link childhood obesity to rising rates of childhood hypertension. In some cases it's due to a problem with the kidneys or other conditions. If no specific cause is found, doctors call it "essential hypertension."

Some medicines (such as steroids or oral contraceptives) can lead to high blood pressure, as can using alcohol and illegal drugs.

If it's not treated, high blood pressure can damage the heart, brain, kidneys, and eyes. But when hypertension is caught early, monitored, and treated, kids can lead an active, normal life.

Why Is High Blood Pressure a Health Problem?

If high blood pressure continues for a long time, the heart and arteries might not work as well as they should. Other organs that are receiving the blood, like the kidneys and brain, also can be harmed.

While high blood pressure doesn't always cause symptoms, it still affects the body and puts a person at risk for long-term health problems. In rare cases, severe hypertension can cause headaches, visual changes, dizziness, nosebleeds, heart palpitations, and nausea.

If your child has severe high blood pressure and has any of these symptoms, get medical care right away.

How Does Blood Pressure Work?

Blood pressure is the force that blood puts on our blood vessel walls as the heart pumps. When the heart contracts and pushes blood into the vessels, blood pressure rises. It lowers when the heart relaxes, but there's always some pressure in the arteries.

Two physical forces drive blood pressure — one force comes from the heart as it pumps blood into the arteries and through the circulatory system, and the other is from the arteries as they resist this blood flow.

Blood pressure changes from minute to minute and is affected by activity and rest, body temperature, diet, emotional state, posture, and medicines.

How Is Blood Pressure Measured?

Health care providers measure blood pressure with a sphygmomanometer (sfig-mo-muh-NAH-muh-ter), which has a cuff that's wrapped around the upper arm and pumped up to create pressure. When the cuff is inflated, it squeezes a large artery in the arm, stopping the blood flow for a moment. Blood pressure is measured as air is gradually let out of the cuff, which allows blood to flow through the artery again.

The doctor or nurse will also put a stethoscope over an artery to hear the first pulse as the blood flows through — this is the systolic pressure (or the pressure at the peak of each heartbeat). The diastolic pressure (the pressure when the heart is resting between beats) is noted when the sounds disappear.

When a blood pressure reading is taken, the higher number represents the systolic pressure and the lower number represents the diastolic pressure. For example: 120/80 (120 over 80) in an adult means that the systolic pressure is 120 and the diastolic pressure is 80. As kids grow, their blood pressure increases from a systolic pressure of about 70–90 (as babies) to adult values (when they're teens).

Automated devices, which are good for screening, also can measure blood pressure, but a manual blood pressure measurement is more accurate.

How Is High Blood Pressure Diagnosed?

All kids should have their blood pressure checked regularly. Doctors usually start measuring blood pressure during routine checkups when kids are 3 years old. So it's important not to miss these appointments, particularly if your child is overweight or there's a family history of high blood pressure.

Diagnosing hypertension in kids can be tricky because it doesn't always cause noticeable symptoms. In kids, high blood pressure is defined as blood pressure greater than the 95th percentile for their age, height, and gender (meaning 95% of kids of the same age, height, and gender will have blood pressure below this number).

Blood pressure varies a lot from day to day, so several blood pressure checks might be done to make a diagnosis (unless the pressure is very high, and then treatment is needed right away).

It's not unusual for a first blood pressure reading to be high if a child is nervous, so the health care provider will likely take three readings, then use an average of the three to determine whether a child has (or is at risk for) high blood pressure.

Some doctors use a test called ambulatory blood pressure monitoring in which a child wears a blood pressure cuff all day to confirm a hypertension diagnosis. It's often more accurate than blood pressure tests in the doctor's office because the child is less likely to be affected by any stress from the office visit.

How Is High Blood Pressure Treated?

If an illness is causing hypertension, treating it might be enough to get the blood pressure back to normal.

Many kids and teens with high blood pressure have an unhealthy lifestyle — a bad diet, excess weight, stress, and too little physical activity. So the health care provider might recommend weight loss, exercise, reduced screen time (time spent watching TV, or using a computer or mobile devices), dietary changes, and even relaxation techniques. Teens with hypertension should not smoke because it can make the long-term associated heart problems worse.

Here's what to focus on:

Weight loss: If your child is overweight, your doctor might recommend an ongoing weight-loss program that includes a minimum of 30 minutes of aerobic exercise every day.

Daily exercise: Being fit is a key part of blood pressure control. All kids with hypertension should exercise and play sports for 1 hour each day — with some activity (like jogging) most days and higher levels of activity (like running) 3 times a week. Usually, exercise is restricted only when hypertension is very severe. Kids with severe hypertension should not do any weight- or power-lifting, bodybuilding, or strength training until their blood pressure is under control and a doctor says it's OK.

Dietary changes: The health care provider might recommend a diet that includes more vegetables (especially leafy green vegetables), fruits, low-fat dairy products, and fiber-rich foods, and fewer carbohydrates, fats, processed foods, and sugary drinks. He or she also might recommend preparing low-sodium dishes and not adding salt to foods. Watch out for foods with lots of hidden salt (like bread, sandwiches, pizza, and many restaurant and fast-food options).

Most health care providers prefer not to prescribe medicine for kids with mild hypertension. However, if lifestyle changes do not bring improvement, medicines might be needed.

Remember, while mild-to-moderate hypertension is rare in kids, over time it can damage the heart, kidneys, and blood vessels. Diagnosing and treating it will help prevent this damage.